Over recent years, by manipulating a micromachine technology and an ultra-microfabrication technology, a system has been developed in which a device and a member (for example, a pump, a valve, a flow channel, and a sensor) for conventional sample preparation, chemical analysis, and chemical synthesis are miniaturized and integrated on one chip (for example, Patent Document 1). This is also referred to as a μ-TAS (Micro Total Analysis System) which is a method in which a member referred to as a microchip is mixed with a specimen (for example, a DNA-treated extracted solution obtained via treatment and extraction of urine, saliva, or blood of a subject to be tested) and a reagent, followed by detection of the resulting reaction to examine characteristics of the specimen.
A microchip is produced in such a manner that a substrate made of a resin material or glass material is subjected to groove processing using a photo-litho process (a method to produce grooves by etching a pattern image using chemicals) or laser light and then provided with a microscopic follow channel capable of passing a reagent and a specimen and a reservoir to store the reagent. Various patterns thereof have been proposed.
When specimen characteristics are examined using such a microchip, liquid such as a reagent and a specimen stored in the microchip are sent into a flow channel using a micropump, whereby the reagent and the specimen are allowed to react together, followed by being introduced into a detection section for detection. In the detection section, the targeted substance is detected, for example, by an optical detecting method.
When liquid is sent into a flow channel of a microchip, in the case of the presence of air bubbles or other gases in the liquid or therebetween, these gases need to be eliminated in some cases in order to carry out mixing by controlling liquid sending and reaction/detection of the liquid.
In view of these problems, Patent Document 2 discloses a micro amount liquid control mechanism in which two ducts are communication-connected by a narrow pipe whose inner wall surface is formed to be hydrophobic. In the micro amount liquid control mechanism, the narrow pipe is formed to be hydrophobic, whereby such a constitution is realized that entering of liquid is inhibited but gas can easily be passed. And, via the pressure difference between the two duct interiors, in one duct, the liquid is controlled at any appropriate position. By shaping the arrangement of a plurality of narrow pipes, gas present between liquid clusters is eliminated, whereby two liquid clusters are mixed together.
Patent Document 3 discloses a micro liquid control device featuring a narrow gap section with a narrow gap formed to be hydrophobic in the same manner. In such a narrow gap, gas can easily be passed but the flow of liquid is controlled by the flow channel resistance thereof Further, in the micro liquid control device, a flow channel to pass liquid is arranged and narrow gap sections to pass gas are arranged on both sides thereof In this manner, such a constitution is realized that the liquid flowing in the central flow channel cannot enter the narrow gap sections of the both sides by flow channel resistance, whereby the liquid and the gas can stably be passed.
Patent Document 1: Unexamined Japanese Patent Application Publication (hereinafter referred to as JP-A) No. 2004-28589
Patent Document 2: JP-A No. 2000-27813 (page 5, FIG. 4)
Patent Document 3: JP-A No. 2006-142242